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The role of epigeic macroarthropod predators in the regulation of abundance and biomass of saprophagous nematodes on grass litter of meadow

Stanuszek S.

Polish Journal of Ecology

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2001

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Vol. 49, nr 1

45-57

EN

Research hypothesis supposed that: 1) microbes, saprophagous nematodes and predacious, epigeic macroarthropods could create the aboveground, detrital food web of meadow; 2) in such food web the top-down regulation of abundance and biomass of saprophagous nematodes and microbes take place in a way predicted by trophic-dynamic theory. A field experiment with manipulation of macroarthropod predators abundance as a method in order to test this hypothesis was chosen. The results were quite opposite to the supposition of the trophic-dynamic theory. Exclusion of epigeic macroarthropods from the supposed food-web results in decreased abundance and biomass of nematodes and increased abundance of bacteria considered as entity. However, it was evident that the top-down regulation of nematode abundance exists there, but its mode is rather behavioral than trophic. Trophic interactions between predacious macroarthropods and nematodes has not been observed there. The macroarthropods served as the transport for the nematodes. In such way they could regulate the initial number of nematodes which colonized the litter.

2

Mineralization and humification of Dactylis glomerata litter in field experiment excluding macroarthropods

Kusińska A., Kajak A.

Polish Journal of Ecology

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2000

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Vol. 48, nr 4

299-310

EN

Decomposition rate of Dactylis glomerata was compared in two types of field mesocosms - (O-open) accessible for macroarthropods active on the grassland soil surface, or not accessible (C-closed) for them. Content of total carbon and nitrogen, as well as carbon incorporated in humus compounds was determined in the litter exposed in litter bags and inside poor in organic matter sandy substratum underlying the litter. Studies were repeated in two experiments, each lasting about a year. At the end of experiments 51-61% of the initial amount of carbon, introduced in the litter was mineralized, 13-19,7% was transformed into humus acids. Mineralization rate was more intense in C mesocosms, higher amount of humus was recorded in mesocosms accessible for macroarthropds (by 2,3 and 14,6% in autumn, respectively in both experiments). This newly formed humus was easily decomposable, part of it, particularly fulvic acids, were mineralized during winter

3

Effect of macroarthropods patrolling soil surface on decomposition rate of grass litter (Dactylis glomerata) in a field experiment

Szanser M.

Polish Journal of Ecology

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2000

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Vol. 48, nr 4

283-297

EN

The rate of grass decomposition was analysed in three field experiments (I, II, and III) in mesocosms where patrolling of area by large epigean invertebrates was unlimited (O - open) or restricted (C - closed). The mesocosm contained soil cores (100 cm^2, 15 cm deep) or were filled with poor substrate (sand with clay) and placed in a meadow soil profile. In Experiment III an additional treatment was applied, i.e. litter manuring with insect faeces (of cockhafer larvae Osmoderma eremita (Scarabeidae) and of locust Locusta migratoria (Oeolipodidae). The last treatment aimed at determining the effect of macrofauna faeces on litter decomposition rate. To exclude influence of roots' ingrowth into the substrate on the rate of litter decay the mesocosms with restricted ingrowth were applied. The litter exposed on the soil surface decayed faster than when exposed on sand. Patrolling of the area by large soil invertebrates had no effect on the litter decay rate during the first 8-13 months from the exposure (Exp. I and II). In the experiment, where litter remained longer in the field, i.e. 24 months (Exp. III), in 13-months after grass exposure it was found that the amount of remaining matter was significantly higher and the daily decay rate was lower in the closed mesocosms than in the open ones. These differences were maintained in the second year up to the end of the experiment. Litter manuring with insects' faeces was clear only in the treatment without root' ingrowth into the substrate.